This invention relates in general to methods of and systems for removing minuscule solid particles from liquid, and more particularly it is concerned with a method of and a system for removing minuscule solid particles from liquid which are suitable for removing cruds (minuscule particulate material produced by corrosion) produced in the liquid handling piping of a nuclear power plant.
Heretofore, it has been customary to use filters of the type precoated with a filtering aid for removing cruds from radioactive waste liquid of a nuclear power plant. Some disadvantages are associated with this type of filters. They include: (1) inability to remove finer minuscule solid particles or cruds, (2) occurrence of obturation of the filters at early stages of use, and (3) an inordinately large proportion of the used filtering aid which is about ten times as high as the removed cruds. In a nuclear power plant, it is necessary that radioactive waste fluid be filtered and recovered for recycling as a cooling water for the core of the reactor. In the event that filters are not usable, removal of cruds should be carried out by using an evaporator unable to increase its processing capacity to the same level as the filters. This would increase running cost and the space required for installation. Moreover, pending final decisions on disposal of wastes from spent fuel, production of wastes at this time would make it necessary to increase spaces for storing such wastes in caskets and cost for solidifying the wastes. To obviate these problems, a demands for filters of improved performance has increased in recent years.
Generally, a porous tube filter is known which is produced by sintering metal powder and comprises a filter element composed of a tube made of metal and formed with tiny openings in its wall. Liquid to be processed is supplied to the porous tube filter, and filtered liquid or filtrate containing no solid particles flows out through the tiny openings to the outer surface of the porous tube filter. The idea of using a porous tube filter for removing cruds from waste liquid of a nuclear power plant has not hitherto been entertained.